Method for producing a contact reed

ABSTRACT

A method for producing a contact reed especially suitable for use in a reed switch to ensure a long life and low electric contact resistance of the switch, comprising electrolytically polishing the reed which is conducted in an electrolyte of H3PO4 being kept at a temperature range of from about 50* C to 60* C under the application of an electric current of from about 2 to 5 A/dm2 for from about 40 to 50 minutes to obtain a reed which will have a slightly rounded and smooth surface after being plated and then plating the electrolytically polished reed. The contact reed made thereby has a flat surface which is free from partial contact and undesirable pits.

United States Patent [1 1 Ono et al.

[ 1 March 6, 1973 METHOD FOR PRODUCING A CONTACT REED [73] Assignees:Nippon Telegraph and Telephone Public Corporation; Hitachi, Ltd.,

both of Tokyo, Japan [22] Filed: Dec. 31, 1970 [21] Appl. No.: 103,144

Related US. Application Data [63] Continuation-impart of Ser. No.723,433, April 23,

3,242,557 3/1966 Ellwood ..29/622 2,227,454 l/l94l Kushner ..204/342,776,255 l/l957 Hammond et al. ..204/l40.5

2,7 30,494 l/ l 956 Bennert ..204/145 R 2,725,353 11/1955 Strobel..204/32 R OTHER PUBLICATIONS Metal Progress, Vol. 49, No. 3, pages537-8 March 1946.

Primary ExaminerJohn l-l. Mack Assistant Examiner-Regan J. FayAttorney-Craig, Antonelli, Stewart and Hill [5 7] ABSTRACT A method forproducing a contact reed especially suitable for use in a reed switch toensure a long life and low electric contact resistance of the switch,comprising electrolytically polishing the reed which is conducted in anelectrolyte of H PO being kept at a temperature range of from about 50 Cto 60 C under the application of an electric current of from about 2 to5 A/drn for from about 40 to 50 minutes to obtain a reed which will havea slightly rounded and smooth surface after being plated and thenplating the electrolytically polished reed. The contact reed madethereby has a flat surface which is free from partial contact andundesirable pits.

25 Claims, 15 Drawing Figures NUMER OF/NTEGRATED FA/LU/PE GOV/N75PATENTEDHAR 51575 3719567 SHEET 10F 4 FIG. I

FIG. 25

FIG. 3A 3 PRIOR ART FIG. 12 k FIG. 13 /00 000 g 00- 600 Em 60- l 0' l(I) 0 l I l l I l I l I INVENTORS Kfizuumqsq 0N0, IHKLLYR TQM, 6EN-1CH|METHOD FOR PRODUCING A CONTACT REED CROSS-REFERENCES TO RELATEDAPPLICATIONS This application is a continuation-in-part of patentapplication Ser. No. 723,433 filed on Apr. 23, 1968, now abandoned,entitled METHOD FOR PRODUC- ING A CONTACT REED.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to methods for producing contact reeds. The term contact reedused in this invention is intended to denote those contact elementsemployed in, for example, a switch which permits the transfer of currentwhen these contact elements are brought into contact with each other.Thus, this invention relates to an improved method for producing acontact reed for use in a switch, and more particularly to a novel andimproved method for producing a contact reed for use in a reed switch inwhich the contact pressure between the contact reeds is very small. Inthe following description, the present invention will be described withspecific reference to contact reeds for use in such a reed switch ratherthan reference to commoner contact reeds used in conventional switches.However, it will be understood that the present invention includes themanufacture of common contact reeds used in conventional switches.

2. Description of the Prior Art A reed switch is a sort of electricalswitch means which comprises a pair of contact reeds of metal materialdisposed opposite to each other in an evacuated glass tube or in a glasstube filled with an inert gas such as argon and is adapted to operate insuch a manner that the pair of metal contact reeds are urged intocontact or released from the contacting state in response to the on-offapplication of an external magnetic field thereby to make or break acircuit. The matter to which the greatest consideration should be givenin connection with the manufacture of a reed switch of the structuredescribed above is how to minimize the electrical contact resistanceappearing in the contact area when the two contact reeds are broughtinto contact with each other, for ifa high electrical contact resistanceshould exist in the contact area, a large voltage drop would take placeacross the contact reeds to give rise to electric discharge or thegeneration of heat in the contact area due to the high resistance. Thesephenomena would give rise to trouble including excessive consumption ofthe contact reeds, deterioration of the material of the reeds, and anunsatisfactory state of contact.

The desired minimization of the contact resistance between the contactreeds of the reed switch has a concern with the material of the contactreeds as well as the contact pressure between the contact reeds, but amore important and decisive factor is the state of surface finish of thecontact reeds. This is because the contact area between the contactreeds will vary greatly depending on the state of surface finish thereofand hence the electrical resistance will correspondingly greatly vary inview of the fact that the state of contact between the contact reeds isa fact-to-face contact.

Therefore, a considerable effort has hitherto been made for thesuccessful manufacture of the contact reeds of the kind described above.One of the conventional manufacturing methods which is likely to be thebest of them comprises the basic steps of pressing to flatten a rawmaterial, cutting a workpiece of suitable length from the flattened rawmaterial, abrasing the workpiece by the barrel method, annealing theworkpiece, subjecting the workpiece to a pretreatment includingelectrolytic cleaning in a solution such as a sodium cyanide solution,supersonic cleaning and chemical cleaning in an aqueous solution of anacid of alkali, and plating the workpiece for the surface finishthereof. In the Prival Patent, US. Pat. No. 3,251,121, which is one ofthe conventional methods, the surface of the workpiece is subjected to apretreatment including a hot acid dip and a vapor phase degreasing formaking a plating of coating materials onto the surface of the workpieceeasy by activating the surface of the workpiece. And also, in theFletcher Patent (U.S. Pat. No. 1,417,896), Kushner Patent (U.S. Pat. No.2,227,454), and Bennert Patent (U.S. Pat. No. 2,730,494), the metalsurface is subjected, for example, to an electrolytic cleaning treatmentby immersing the metal in an acid bath containing a salt of copper, to asolution of hydrofluosilicic acid, or to an anodic treatment in asolution of hydrochloric acid and water for cleaning the metal surfaceso that a firm and coherent coating of the deposited metal can bedirectly obtained on the metal surface, for cleaning all of the oxide onthe metal surface so that the coating material may cling, for removing aburr from the metal, or for forming a clean, bright surface of themetal.

However, the greatest defect of the contact reed manufactured inaccordance with such methods resides in the fact that the longitudinaland edges of the contact reed are thickly plated to have a largerthickness than the remaining portions and thus the contact reed has asurface contour which is concaved at the central portion thereof. Such asurface contour is undesirable for the contact reeds when they are usedin a switch because non-uniformity or partial contact is produced in thecontact area resulting in an incomplete contact between the contactreeds which are brought into contact with each other in the switchingoperation. Furthermore, very fine impurity particles of an abrasive suchas A1 0 Cr O or SiO employed in the abrasing step are forced into thecontact reed and these impurity particles cannot be removed even withthe cleaning step following the abrasing step. Such an impurity preventsthe otherwise satisfactory deposition of the plating layer and wouldproduce undesirable pits in the contact surface and cause a resultantincrease in the electrical contact resistance. Moreover, the partialcontact between the contact reeds would give rise to a larger degree ofwear at that portion of the contact reeds and reduce the service life ofthe contact reeds. Further, in the conventional methods, the metalsurface was only cleaned or strongly etched since the electric currentin the pretreatment was too small or too large to etch the surface ofthe metal. As the result of the strong etching, the metal surface becamerough.

SUMMARY OF THE INVENTION It is therefore a primary object of the presentinvention to provide a method for producing a contact reed which has asurface contour giving a small contact resistance and is substantiallyfree from wear thus having a long service life.

A further object of the present invention is to provide a method formanufacturing a contact reed which is free from the undesirable partialcontact at the longitudinal end edges thereof and has a uniformly platedfinished surface free from the presence of objectionable pits therein.

These and other objects, advantages and features of the presentinvention will be more apparent from the following detailed descriptionwith reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic perspective viewshowing the shape of a contact reed blank which is obtained by pressingto flatten the raw material in the form of a wire and then cutting apiece of suitable length from the flattened wire.

FIG. 2A is a schematic perspective view of a contact reed produced bythe method embodying the present invention.

FIG. 2B is a sectional view taken on the line XX in FIG. 2A.

FIG. 3A is a schematic perspective view showing the external shape of aconventional contact reed produced by the prior method including thestep of abrasing by the barrel method.

FIG. 3B is a sectional view taken on the line Y-Y in FIG. 3A.

FIG. 4 is a microphotograph enlarged at a magnification of 1000 timesshowing the surface state of a contact reed after it has been subjectedto electrolytic polishing according to the method of the presentinvention.

FIG. 5 is a microphotograph enlarged at a magnification of 1,000 timesshowing the surface state of a conventional contact reed after it hasbeen subjected to barrel abrasing according to the prior method.

FIG. 6 is a microphotograph enlarged at a magnification of 1,000 timesshowing the surface state of the conventional contact reed after it hasbeen subjected to barrel abrasing and then to annealing.

FIGS. 7 to 9 are microphotographs showing the sur face state of theconventional contact reed after it has been subjected to barrel abrasingaccording to the prior method, the microphotographs being taken by anX-ray microanalyzer at a magnification of 1,000 times, wherein FIG. 7represents a microphotograph taken with Al-characteristics rays, FIG. 8represents a microphotograph taken with O -characteristics rays and FIG.9 represents a microphotograph taken with F e-characteristics rays.

FIGS. 10 and 11 are microphotographs showing the surface state of thecontact reed produced by the method of the present invention and theconventional one produced by the prior method, respectively, themicrophotographs being taken at a magnification of 60 times.

FIG. 12 is a graphic illustration of the number of integrated failurecounts relative to the number of switching times in the conventionalcontact reed obtained by the prior method.

FIG. 13 is a graphic illustration of the survive ratio of stick failurerelative to the number of switching times in the conventional contactreed obtained by the prior method.

DESCRIPTION OF THE PREFERRED EMBODIMENT The method according to thepresent invention is entirely the same as the prior method describedpreviously in that it also comprises the initial steps of pressing toflatten a raw material in the form of a wire and cutting a piece ofsuitable length from the flattened wire to obtain a blank or workpieceof a shape as seen in FIG. 1. However, the present invention differs inthe subsequent steps from the prior method which includes abrasing theworkpiece by the barrel method and then plating the workpiece to coverit with a metal layer. More precisely, the present invention ischaracterized by the steps of rough polishing the workpiece by thebarrel method, annealing the workpiece, electrolytically polishing atleast the contact portion of the annealed workpiece to such an extentthat the workpiece after being plated will have a slightly rounded andsmoothed surface, and finally plating the workpiece to obtain a contactreed.

In case of necessity, before plating the workpiece is subjected to apretreatment including electrolytic cleaning in a solution such as asodium cyanide solution, supersonic cleaning and chemical cleaning in anaqueous solution of an acid or alkali for activating the surface of theworkpiece.

The contact reed produced in accordance with the method of the presentinvention described above has its longitudinal end edges rounded off andhas its contact surface 1 shaped to a planar form having very gentleconvex roundness all over as seen in FIGS. 2A and 2B. Thus, the contactreed obtained in accordance with the present invention differsdistinctly from the prior contact reed structure which is thickened atlongitudinal end edges 2 and has its contact surface 3 formed as aconcave plane as seen in FIGS. 3A and 3B.

The concave contact surface and the thickened longitudinal end edges inthe prior contact reed structure are considered to result from the factthat the end edge portions are more thickly plated than the remainingflat portions in the plating step due to an extremely higher currentdensity at the end edge portions than at the remaining flat portions andthe end edge portions are electrolytically removed more than theremaining flat portions in the subsequent electrolytic polishing step.In contrast, the electrolytic polishing step is followed by the finishplating step according to the method of the present invention.Accordingly, the metal portion removed from the end edges of theworkpiece is substantially offset by the coating portion subsequentlyadded to the end edges of the workpiece, and the contact reed finallyobtained can be shaped to have a surface contour of very gentle convexroundness all over.

The gently convexly rounded shape ensures a sufficient contact areadesired for the contact reed even if the contact reed may be somewhatincorrectly mounted and thus reduces the possibility of the contactresistance becoming excessively high. Furthermore, the gently convexlyrounded shape eliminates unusual wear which may take place due tonon-uniform or partial contact between a pair of contact reeds, therebycorrespondingly extending the service life of the contact reeds.

The present invention will now be described in more detail by referenceto a practical example.

A wire which is a raw material of the contact reed is pressed to flattento a thickness in the order of 0.2 mm by a conventional press machinesuch as a hydraulic press. A workpiece of suitable length, for example,1 to 3 cm long is cut from the flattened wire and is then shaped toapproximate dimensions by rough polishing by the barrel method. Theapproximately shaped workpiece is then annealed to remove the stressproduced during the pressing, and is subsequently subjected toelectrolytic polishing. The electrolyte suitable for this purpose may beH PO H 80 I-lCr O or any other electrolyte conventionally employed inelectrolytic polishing. After the electrolytic polishing, waterremaining on the workpiece must be removed. Removal of water cansubstantially be attained by heating the workpiece for about 3 minutesat about 200 C. The temperature of the electrolyte in the electrolyticpolishing should desirably be of the order of 40 to 90 C., and thecurrent density should desirably be of the order of l to amperes persquare decimeter, and the duration of current supplied is desirably ofthe order of 30 to 60 minutes. The electrolysis will proceed extremelyslowly and an undesirable reduction in the industrial productivity wouldresult in case the temperature and the current supply are less than theabovespecified values. Moreover, in case the temperature and the currentsupply exceed the above-specified values, the electrolysis will proceedvery quickly and the contact reed to be worked will have a roughsurface, which gives rise to the defect of an unsatisfactory state ofcontact and an increase in the contact resistance. Contact reeds havingremarkably excellent operating characteristics could be obtained whenthe temperature of the electrolyte, and the current density and theduration of current supply were set at 50 to 60 C. and 2 to 5 amperesper square decimeter and 40 to 50 minutes, respectively. The workpiecesubjected to electrolytic polishing in the above manner is then platedwith gold or silver to obtain a contact reed which is free from pits oflike objectionable spots and has a very smooth surface.

In the photographic representations of the microstructure of the contactreed given in FIGS. 4 to 11, the contact reed is made from a 52 Ni 48 Fealloy.

FIG. 4 represents a microphotograph enlarged at a magnification of 1,000times showing the surface state of the contact reed after it has beensubjected to electrolytic polishing in accordance with the method of thepresent invention. It will be seen from FIG. 4 that the contact reed hasa very smooth surface.

FIGS. 5 and 6 represent microphotographs enlarged at a magnification of1,000 times showing the surface state of a conventional contact reedafter it has been subjected to abrasing by the barrel method and then toannealing treatment in accordance with the prior method, respectively.Black spots seen in FIGS. 5 and 6 are particles of alumina (A1 0 used asan abrassive, and thus it will be seen that the conventional contactreed has a very rough surface state compared with the surface state ofthe contact reed according to the present invention shown in FIG. 4.

FIGS. 7 to 9 represent microphotographs taken by an X-ray microanalyzerto investigate the surface state of the conventional contact reed afterit has been subjected to abrasing by the barrel method in accordancewith the prior method. Spots seen in FIGS. 7 to 9 apparently indicatethe fact that impurity particles of the abrasive become attached to thesurface of the contact reed. The microphotographs shown in FIGS, 7 to 9are taken with Al-characteristics rays, O -characteristics rays andFe-characteristics rays, respectively. These microphotographs verify thefact that the particles of alumina used as the abrasive attach to thesurface of the contact reed and the rough surface state as seen in FIG.5 or 6 is thereby formed.

FIG. 10 represents a microphotograph enlarged at a magnification oftimes showing the surface state of the contact reed after it has beensubjected to the electrolytic polishing and then to finish platingtreatment in accordance with the method of the present invention. Thecentral part designated by the reference character A indicates theportion with which the contact reed contacts an opposite contact reed,and it will thus been seen that the contact reed is provided with such awide contact area.

In contrast, as seen in FIG. 11 representing a microphotograph enlargedat a magnification of 60 times, the conventional contact reed madeaccording to the prior method contacts with an opposite contact reed bya plurality of partial contact portions B, and thus the conventionalcontact reed has an extremely undesirable surface state.

From a mere glance at FIGS. 4 to 11, it will be understood that themethod according to the present invention is far superior to the priormethod.

The performance of a reed switch employing the contact reed madeaccording to the present invention will be described hereunder. Typicalindices represent ing the performance of a reed switch include (1) thenumber of integrated failure counts and (2) the survive ratio of stickfailure in percent. In seeking the number of integrated failure counts,five reed switches are connected in series and every occasion on whichthe total contact resistance of these reed switches exceeds one ohm iscounted as a failure. In seeking the survive ratio of stick failure, anoperation circuit including a multiplicity of reed switches having avoltage applied across the contact reeds thereof is prepared, and thesereed switches are simultaneously energized. Those contact reeds on whichstick-like projections are formed due to electric discharge are removedas rejections, and the ratio of the number of the remaining normalcontact reeds to the number of all the contact reeds employed is soughtto obtain the survive ratio of stick failure in per cent.

As will be apparent from the characteristic shown in FIG. 12, the numberof integrated failure counts in the case of the conventional contactreed made according to the prior method shows an abrupt increase at thenumber of switching times of 17 to 19 millions, and as will be alsoapparent from the characteristic shown in FIG. 13, the survive ratio ofstick failure shows an abrupt decrease at the number of switching timesof 7 to 8 millions. In the case of the contact reed made according tothe method of the present invention, it is to be noted that anexperiment is still in progress in which the reed switch has alreadybeen turned on-off more than 40 million times without any increase inthe number of integrated failure counts and any decrease in the surviveratio of stick failure.

We claim:

1. A method for producing a contact reed usable as a conductor elementin a contact device, said reed having a contact portion covered with acontact coating of a conductive material, which comprises the steps of:cutting out a workpiece from an iron-containing conductor metal andshaping it into aflat elongated shape; polishing said shaped workpieceto clean up the surface thereof; annealing said polished workpiece toremove the stress existing therein; electrolytically polishing saidannealed workpiece at least on a predetermined portion thereof which isto be provided later with a conductive coating thereon for sufficienttime to slightly round off the elongated end edges of said workpiece inan electrolyte conventionally employed in electrolytic polishing; andthereafter electrically metal plating over the polished surface of saidworkpiece to provide a contact metal coating on said predeterminedportion of said workpiece and to obtain a contact reed having a contactportion with a substantially flat surface.

2. A method for producing a contact reed according to claim 1, in whichsaid electrolytic polishing is conducted with a current of about 1 to 10A/dm in an electrolyte heated to a temperature of 40 to 90 C.

3. A method for producing a contact reed according to claim 2, whereinsaid current is from about 2 to A/dm and said temperature is from about50 to 60 C.

4. A method for producing a contact reed according to claim 3, whereinsaid electrolytic polishing is conducted for from about 30 to 60minutes.

5. A method according to claim 4, wherein said electrolytic polishing isconducted in an electrolyte selected from the group consisting of H PO H80 and HCr O 6. A method for producing a contact reed according to claim3, wherein said electrolytic polishing is conducted for from about 40 to50 minutes.

7. A method for producing a contact reed according to claim 6, whereinsaid electrolytic polishing is conducted in an electrolyte of H PO 8. Amethod according to claim 1, wherein said electrolytic polishing isconducted in an electrolyte selected from the group consisting of H PO HSO and HCr O 9. A method for producing a contact reed according to claim1, wherein the workpiece is electrolytically polished for a sufficienttime to obtain a convex shape.

10. In a method for producing a contact reed having a contact portioncovered thereon with a contact coating of conductive metal, theimprovement which comprises the steps of: electrolytically polishing apredetermined portion of a flat elongated workpiece made'of aniron-containing metal which is to be coated later with a conductivemetal layer for a sufficient time to slightly round off the elongatedend edges of said predetermined portion of the workpiece in anelectrolyte conventionally employed in electrolytic polishing; andthereafter electrically metal plating over the polished surface at leaston the predetermined portion of said workpiece so as to coat saidportion with a conductive metal layer, and to obtain a substantiallyflat conductive metal coating on the workpiece.

11. A method for producing a contact reed according to Claim 10, inwhich said electrolytic polishing is conducted with a current of about 1to A/dm in an electrolyte heated to a temperature of 40 to 90 C.

12. A method for producing a contact reed according to claim 11, whereinsaid current is from about 2 to 5 A/dm and said temperature is fromabout 50 to 60 C.

13. A method for producing a contact reed according to claim 12, whereinsaid electrolytic polishing is conducted for from about 30 to 60minutes.

14. A method according to claim 13, wherein said electrolytic polishingis conducted in an electrolyte selected from the group consisting of HPO H and HCr O 15. A method for producing a contact reed according toclaim 12, wherein said electrolytic polishing is conducted for fromabout 40 to 50 minutes.

16. A method according to claim 10, wherein said electrolytic polishingis conducted in an electrolyte selected from the group consisting of HP0 H 80, and HCr O 17. A method for producing a contact reed accordingto claim 10, wherein the workpiece is electrolytically polished for asufficient time to obtain a convex shape.

18. A method for producing a contact reed usable as a conductor elementin a contact device, said reed having a contact portion covered with acontact coating of a conductive material, which comprises the steps of:cutting out a workpiece from an iron-nickel alloy and shaping it into anelongated flat shape; polishing said shaped workpiece to clean up thesurface thereof; annealing said polished workpiece to remove the stressexisting therein; electrolytically polishing said annealed workpiece atleast on a predetermined portion thereof which is to be provided laterwith a conductive coating thereon in an electrolyte selected from thegroup consisting of H PO H 80 and l-lCr O heated to a temperature of 40to C. with a current of about 1 to l 0 A/dm for from about 30 to 60minutes, and thereafter electrically plating a contact coating of aconductive material selected from the group consisting of gold andsilver over the polished surface of said workpiece.

19. A method according to claim 18, wherein said electrolytic polishingis conducted in an electrolyte of H PO 20. A method for producing acontact reed according to claim 18, wherein said electrolyticallypolishing is conducted in an electrolyte selected from the groupconsisting of H PO H 80 and HCr O heated to a temperature of 50 to 60 Cwith a current of about 2 to 5 A/dm for from about 40 to 50 minutes.

21. A method according to claim 20, wherein said electrolyticallypolishing is conducted in an electrolyte of H PO 22. In a method forproducing a contact reed having a contact portion covered thereon with acontact coating of conductive material, the improvement which comprisesthe steps of: electrolytically polishing a predetermined portion ofworkpiece which is to be coated later with a conductive material layerin an electrolyte selected from the group consisting of H PO H 80, andHCr O heated to a temperature of 40 to 90 C with a current of about 1 to10 A/dm for from about 30 to 60 minutes; and thereafter electricallyplating a contact coating of a conductive material selected from thegroup consisting of gold and silver over the polished surface at leaston the predetermined portion of said reed.

ing to claim 22, wherein said electrolytically polishing is conducted inan electrolyte selected from the group consisting of H PO.,, H 80 andl--lC1' O heated to a temperature of 50 to 60 C with a current of about2 to 5 A/dm for from about 40 to 50 minutes.

25. A method according to claim 24, wherein said electrolyticallypolishing is conducted in an electrolyte of H PO

1. A method for producing a contact reed usable as a conductor elementin a contact device, said reed having a contact portion covered with acontact coating of a conductive material, which comprises the steps of:cutting out a workpiece from an iron-containing conductor metal andshaping it into a flat elongated shape; polishing said shaped workpieceto clean up the surface thereof; annealing said polished workpiece toremove the stress existing therein; electrolytically polishing saidannealed workpiece at least on a predetermined portion thereof which isto be provided later with a conductive coating thereon for sufficienttime to slightly round off the elongated end edges of said workpiece inan electrolyte conventionally employed in electrolytic polishing; andthereafter electrically metal plating over the polished surface of saidworkpiece to provide a contact metal coating on said predeterminedportion of said workpiece and to obtain a contact reed having a contactportion with a substantially flat surface.
 2. A method for producing acontact reed according to claim 1, in which said electrolytic polishingis conducted with a current of about 1 to 10 A/dm2 in an electrolyteheated to a temperature of 40* to 90* C.
 3. A method for producing acontact reed according to claim 2, wherein said current is from about 2to 5 A/dm2 and said temperature is from about 50* to 60* C.
 4. A methodfor producing a contact reed according to claim 3, wherein saidelectrolytic polishing is conducted for from about 30 to 60 minutes. 5.A method according to claim 4, wherein said electrolytic polishing isconducted in an electrolyte selected from the group consisting of H3PO4,H2SO4, and HCr2O4.
 6. A method for producing a contact reed according toclaim 3, wherein said electrolytic polishing is conducted for from about40 to 50 minutes.
 7. A method for producing a contact reed according toclaim 6, wherein said electrolyTic polishing is conducted in anelectrolyte of H3PO4.
 8. A method according to claim 1, wherein saidelectrolytic polishing is conducted in an electrolyte selected from thegroup consisting of H3PO4, H2SO4, and HCr2O4.
 9. A method for producinga contact reed according to claim 1, wherein the workpiece iselectrolytically polished for a sufficient time to obtain a convexshape.
 10. In a method for producing a contact reed having a contactportion covered thereon with a contact coating of conductive metal, theimprovement which comprises the steps of: electrolytically polishing apredetermined portion of a flat elongated workpiece made of aniron-containing metal which is to be coated later with a conductivemetal layer for a sufficient time to slightly round off the elongatedend edges of said predetermined portion of the workpiece in anelectrolyte conventionally employed in electrolytic polishing; andthereafter electrically metal plating over the polished surface at leaston the predetermined portion of said workpiece so as to coat saidportion with a conductive metal layer, and to obtain a substantiallyflat conductive metal coating on the workpiece.
 11. A method forproducing a contact reed according to Claim 10, in which saidelectrolytic polishing is conducted with a current of about 1 to 10A/dm2 in an electrolyte heated to a temperature of 40* to 90* C.
 12. Amethod for producing a contact reed according to claim 11, wherein saidcurrent is from about 2 to 5 A/dm2 and said temperature is from about50* to 60* C.
 13. A method for producing a contact reed according toclaim 12, wherein said electrolytic polishing is conducted for fromabout 30 to 60 minutes.
 14. A method according to claim 13, wherein saidelectrolytic polishing is conducted in an electrolyte selected from thegroup consisting of H3PO4, H2SO4 and HCr2O4.
 15. A method for producinga contact reed according to claim 12, wherein said electrolyticpolishing is conducted for from about 40 to 50 minutes.
 16. A methodaccording to claim 10, wherein said electrolytic polishing is conductedin an electrolyte selected from the group consisting of H3PO4, H2SO4 andHCr2O4.
 17. A method for producing a contact reed according to claim 10,wherein the workpiece is electrolytically polished for a sufficient timeto obtain a convex shape.
 18. A method for producing a contact reedusable as a conductor element in a contact device, said reed having acontact portion covered with a contact coating of a conductive material,which comprises the steps of: cutting out a workpiece from aniron-nickel alloy and shaping it into an elongated flat shape; polishingsaid shaped workpiece to clean up the surface thereof; annealing saidpolished workpiece to remove the stress existing therein;electrolytically polishing said annealed workpiece at least on apredetermined portion thereof which is to be provided later with aconductive coating thereon in an electrolyte selected from the groupconsisting of H3PO4, H2SO4 and HCr2O4 heated to a temperature of 40* to90* C. with a current of about 1 to 10 A/dm2 for from about 30 to 60minutes, and thereafter electrically plating a contact coating of aconductive material selected from the group consisting of gold andsilver over the polished surface of said workpiece.
 19. A methodaccording to claim 18, wherein said electrolytic polishing is conductedin an electrolyte of H3PO4.
 20. A method for producing a contact reedaccording to claim 18, wherein said electrolytically polishing isconducted in an electrolyte selected from the group consisting of H3PO4,H2SO4 and HCr2O4 heated to a temperature of 50* to 60* C with a currentof about 2 to 5 A/dm2 for from about 40 to 50 minutes.
 21. A methodaccording to claim 20, wherein said electrolytically polishing isconducted in an electrolyte of H3PO4.
 22. In a method for producing acontact reed having a contact portion covered thereon with a contactcoating of conductive material, the improvement which comprises thesteps of: electrolytically polishing a predetermined portion ofworkpiece which is to be coated later with a conductive material layerin an electrolyte selected from the group consisting of H3PO4, H2SO4 andHCr2O4 heated to a temperature of 40* to 90* C with a current of about 1to 10 A/dm2 for from about 30 to 60 minutes; and thereafter electricallyplating a contact coating of a conductive material selected from thegroup consisting of gold and silver over the polished surface at leaston the predetermined portion of said reed.
 23. A method according toclaim 22, wherein said electrolytic polishing is conducted in anelectrolyte of H3PO4.
 24. A method for producing a contact reedaccording to claim 22, wherein said electrolytically polishing isconducted in an electrolyte selected from the group consisting of H3PO4,H2SO4 and HCr2O4 heated to a temperature of 50* to 60* C with a currentof about 2 to 5 A/dm2 for from about 40 to 50 minutes.